FIELD OF THE INVENTION
The instant invention relates generally to thermometer strips and more specifically to thermometer strips for liquefied gas tanks which display both the temperature and the internal vapor pressure of the gas.
Many commercial, industrial and medical processes require the use of gaseous materials, thus requiring transportation and storage. Gases such as nitrous oxide (N.sub.2 O) can be liquefied under pressure, greatly reducing the volume occupied and resulting in decreased transportation and storage costs. An additional benefit is that compressed liquefied nitrous oxide will exhibit a constant vapor pressure as the gas is removed from the container, until the point where all of the liquid has been vaporized. The internal vapor pressure of the container, however, is affected by temperature. Many uses require that the gas be released at a fairly specific pressure; for these utilities, it is important to maintain the temperature of the container at a constant temperature. One method of tracking the temperature of the storage container is by affixing a thermometer strip to the exterior surface of the container. Unfortunately, this provides no direct information regarding the internal vapor pressure, which is actually the characteristic of interest.
The present invention provides a dual display temperature/pressure gauge which measures the temperature of the container and displays both the temperature and the calculated vapor pressure of the gas.